1. Field of the Invention
The present invention relates to a radiation image capturing apparatus including a malfunction detecting means for detecting a malfunction of a radiation image generating means, a radiation dose information detector, or a radiation source. The present invention also relates to a method of detecting a malfunction of such a radiation image capturing apparatus.
2. Description of the Related Art
In the medical field, there have widely been used radiation image capturing apparatuses, which apply radiation emitted from a radiation source to a subject. Such apparatus then detect the radiation that has passed through the subject with a radiation detector, and record radiation image information based on the detected radiation.
The radiation image capturing apparatuses of the type described above are required to achieve a good level of radiation image quality, while minimizing the radiation dose applied to the subject (patient). In order to acquire appropriate radiation image information of a region of interest (ROI), it is necessary to establish an exposure control condition, for the purpose of applying a desired dose of radiation to the region of interest.
Japanese Laid-Open Patent Publication No. 10-284289 discloses an X-ray system including an AEC (Automatic Exposure Control) sensor (radiation dose information detector) serving as a detector for automatic exposure control, which is disposed behind a solid-state detector (radiation image generating means) for detecting radiation emitted from a radiation source and generating a radiation image based on the detected radiation. The dose of radiation emitted from the radiation source is controlled based on the radiation dose detected by the AEC sensor.
Radiation detectors, including the solid-state detector and the AEC sensor used in the radiation image capturing apparatus, may possibly suffer from sensitivity malfunctions characterized by fluctuations of an output value thereof (an output signal level or an output current value) with respect to an expected value. Alternatively, the radiation detectors may have normal sensitivity, but the radiation source may possibly suffer from output malfunctions.
These malfunctions may reliably be detected and specified by a separate instrument such as a radiation dosimeter or the like, for example, for measuring the radiation output level. However, if an existing radiation image capturing apparatus does not incorporate such a radiation dosimeter therein, then the radiation image capturing apparatus will require extra expenditures of expense and time in order to connect and adjust the added radiation dosimeter. A radiation image capturing apparatus with a built-in radiation dosimeter, however, is costly due to the presence of the built-in radiation dosimeter.